Aims
of
Study:
Cyclophosphamide, an anti-neoplastic agent, produces
severe
haemorrhagic
cystitis
in
humans
via
a
metabolite,
acrolein,
that
is
excreted
in
urine
(1).
Cyclophosphamide
induced
cystitis
in
rats
is
characterised
by
detrusor
hyperactivity
and
oedema
(2).
Since
bladder
hyperactivity
results
from
in
vivo
metabolism
of
cyclophosphamide
to
acrolein,
urinary
bladder
acrolein
concentrations
may
vary,
depending
on
the
strain
of
rat
as
well
as
factors
that
modulate
liver
microsome
activity,
hydration
and
renal
blood
flow. In order to minimise the effects of such variables,
a
model
in
which
acrolein
is
infused
directly
into
the
bladder
was
developed.
Methods:
Female Sprague Dawley rats were anaesthetised with
isoflurane
(2.5%
at
2
L/min)
and
urethane
(1.2
g/kg,
s.c.). The dome of the bladder was cannulated with
fluid-filled
PE-50
tubing
and
a
venous
port
was
established. Rats were then placed on a heating pad (37oC)
and
the
bladders
were
perfused
with
saline
or
acrolein
in
a
buffer
containing
citric
acid
(50
mM,
pH
5.2)
at
a
rate
of
100
ml/min for up to 6 h.
Bladder
pressure
was
monitored
using
a
Gould
polygraph
and
Power
Lab
data
acquisition
system.
Results:
During baseline saline infusion, the mean urinary
bladder
contraction
amplitude
was
24.5
± 1.9 mmHg (n = 66) and the bladder inter-contraction
interval
was
6.3
± 0.36 min (n = 66). Direct infusion of acrolein (100, 200, 300
and
600
mM) into the bladder produced a dose-dependent
increase
in
contraction
amplitude
and
decrease
in
inter-contraction
interval.
Significant
changes
(p
<
0.01)
in
steady
state
amplitude
and
inter-contraction
interval
readings
were
achieved
after
2
h
of
acrolein
(200
or
300
mM) infusion. The effects of a 1 h acrolein (200 or 300 mM) infusion into the bladder were
not
reversed
by
a
subsequent
3-h
saline
infusion. Acrolein-induced changes in amplitude and inter-contraction interval
were
modulated
by
administration
of
test
compounds. Atropine (1 mg/kg, i.v.) significantly (p <
0.01)
decreased
amplitude
without
affecting
inter-contraction
interval.
The
ganglionic
blocking
agent,
hexamethonium
(0.03,
0.3,
3
mg/kg,
i.v.)
significantly
(p
<
0.05)
decreased
both
amplitude
and
inter-contraction
interval. By contrast, the cyclooxygenase inhibitor,
indomethacin
(0.3,
1,
and
6
mg/kg,
i.v.),
significantly
(p
<
0.01)
decreased
contraction
amplitude
while
significantly
increasing
inter-contraction
interval.
Upon
histopathological
examination
of
the
urinary
bladder,
there
was
diffuse,
transmural
acute
inflammation
characterised
by
severe
oedema,
venular
congestion,
urepithelial
ulceration
and
minor
inflammatory
cell
infiltration.
Conclusions
Acrolein infused directly into the urinary bladder
of
anaesthetised
rats
produces
a
dose-dependent
decrease
in
bladder
inter-contraction
interval
and
an
increase
in
bladder
contraction
amplitude.
The
effects
of
acrolein
last
for
at
least
3h
following
cessation
of
acrolein
administration. Administration of atropine, hexamethonium or
indomethacin
differentially
affected
acrolein-induced
changes
in
bladder
activity.
These
results
suggest
that
a
model
of
acrolein-induced
urinary
bladder
hyperactivity
in
anaesthetised
rats
may
be
useful
in
evaluating
novel
pharmacologic
agents
for
treatment
of
overactive
bladder.
References
1.
Cyclophosphamide
and
urinary
bladder
toxicity
(1961)
Cancer
Research
21: 1577-1589.
2. Cyclophosphamide cystitis
in
rats: involvement of capsaicin-sensitive primary
afferents
(1992)
J.
Auton.
Ner.
Sys.,
38:
201-208.
